There are a variety of reaction systems where a feed component of the reaction is delivered as a fine aerosol mixture of a solution of the component. One such context is flame spray pyrolysis (FSP), in which the fine aerosol mixture is sprayed into the flame area where thermochemical reactions take place. There are a number of devices for producing fine aerosol mixtures, including atomisers, mist makers and two-fluid nozzles. It is typical for these devices to have been optimised for a set of particular working parameters or conditions. As a result, the mean droplet sizes of the aerosol mixture emitted by a given device is more or less a fixed value, depending upon those working parameters or conditions and on the specific design of the device. Moreover, the flow rate of these devices is usually substantially fixed and unable to be altered.
This lack of flexibility and adjustability in the aerosol delivery limits the utility of the reaction systems beyond the bench top or specific tailored applications. An example of a reaction system requiring an aerosol feed is co-pending international patent publication WO 2010/118480 by one of the co-applicants, which discloses a process for depositing nanostructured material onto a particulate substrate. In the preferred method, the nanostructured material is produced by flame spray pyrolysis of an atomised dispersion of micro-dimensional droplets containing a nanophased precursor material.
This process has been proven in principle but there is an opportunity to adapt it to permit low cost commercial production of nanoparticle coatings with tailored properties. A core requirement for such an adaptation is an atomising or droplet generation system able to produce aerosol mixtures of organic or inorganic liquids of variable droplet size, yet narrow droplet size distribution, and variable flow rates. This latter preference arises because different chemical compounds would require different residence times for a complete thermo-chemical reaction.
It is an object of the invention to provide a droplet generation system that at least in part meets this requirement.
Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.